1. Field of the Invention
The present invention relates to a control system or method for controlling the auxiliary section splitter actuator of an automated or partially automated vehicular compound transmission. In particular, the present invention relates to a control system or method for controlling the splitter section actuator of an automated or partially automated compound vehicular transmission wherein a two-position fluid actuated actuator is utilized to engage and disengage non-synchronized jaw clutches to selectively engage either a low-speed or a high-speed splitter section ratio.
2. Description of the Prior Art
Compound change gear transmissions of the type having one or more auxiliary sections connected in series with a main transmission section are very well known in the prior art. Such transmissions are typically associated with heavy duty vehicles such as large trucks, tractor/semi-trailers, and the like. Auxiliary transmission sections are of three general types; range type, splitter type, or combined range/splitter type.
In compound transmissions having a splitter type auxiliary section, the ratio steps of the splitter auxiliary section are less than the ratio steps of the main transmission section and each main transmission section ratio may be split, or subdivided, by the splitter section. Examples of compound change gear transmissions having splitter type auxiliary sections may be seen by reference to U.S. Pat. Nos. 4,290,515; 3,799,002; and 4,527,447, the disclosures of which are hereby incorporated by reference.
In a combined range and splitter type auxiliary section, or sections, both range and splitter type ratios are provided allowing the main transmission to be progressively shifted through its ratios in at least two ranges and also allowing the main transmission section ratios to be split in at least one range. Examples of compound transmissions having a single combined range/splitter type auxiliary section may be seen by reference to U.S. Pat. Nos. 3,283,613; 3,648,546 and 4,754,665; the disclosures of which are hereby incorporated by reference. Assignees well known RT/RTO 11613 and RT/RTO 14718 "Eaton Roadranger" transmissions are examples of combined range/splitter type transmissions.
Another example is the "Ecosplit" model of transmission sold by Zahnradfabrik Friedrichshafen Aktiengeseushaft of Friedrichshafen, Germany which is a sixteen forward speed type of transmission which utilizes a separate two-speed splitter auxiliary section in front of and a separate two-speed range section behind the main transmission section.
It should be noted that the terms main and auxiliary sections are relative and that the designations of the main and auxiliary sections are reversed, the type of auxiliary section (either range or splitter) will also be reversed. In other words, given what is conventionally considered to be a four speed main section with a two-speed range type auxiliary section, if the normally designated auxiliary is considered the main section, then the normally designated main section would be considered a four speed splitter type auxiliary section therefor. By generally accepted transmission industry convention, and as used in this description of the invention, the main transmission section of a compound transmission is that section which contains the largest (or at least no less) number of forward speed ratios, which allow selection of a neutral position, which contains the reverse ratio(s) and/or which is shifted (in manual or semi-automatic transmissions) by manipulation of the shift bar or shift rail or shift shaft/shift finger assembly as opposed to master/slave valve/cylinder arrangements or the like.
Splitter shift control systems and methods for controlling the fully or partially automated shifting of splitter section nonsynchronized jaw clutches in automated or partially automated compound transmissions are known in the prior art. An example of such a partially automated transmission system may be seen by reference to U.S. Pat. No. 4,722,248, the disclosure of which is hereby incorporated by reference. Such prior art automated or partially automated transmissions, especially those utilizing a two-speed splitter section wherein either a low-speed or a high-speed splitter ratio could be selected, utilized a fluid pressure operated differential area piston actuator wherein the smaller piston surface area is constantly pressurized to urge the actuator to cause engagement of the low-speed splitter section ratio and the actuator chamber associated with the larger area piston face is selectively pressurized or exhausted to cause engagement or disengagement of the high-speed splitter section ratio.
The splitter section control systems/methods of the prior art was not totally satisfactory as shifts were occasionally noisy due to splitter clutch raking, in cold weather conditions disengagement of the low-speed splitter clutch was difficult as the full force generated by the larger piston surface was not available and, in the event of a failure of the electricity to the solenoid controllers, the splitter section would automatically default to the low-speed ratio thereof regardless of the intention of the operator.